1. Field of the Invention
The present invention relates generally to means and methods for addressing networked devices in networking systems. Specifically, the present invention relates to apparatus, systems, and methods for managing addresses, priority schemes and device locations in arbitrated loop networks.
2. Description of the Related Art
Arbitrated loop topology may be used to interconnect devices via a network loop that connects the transmit output port of one device to the receive port of the next device in the loop. Typically, each device on the loop must have a unique address in order to communicate on the network. In many arbitrated loop networks, address assignments are automatically determined. At loop initialization, or in response to removal or insertion of a device, the loop may undergo an address assignment process known as address arbitration.
Arbitrated loop networks may support both hard and soft assigned addressing. Hard addresses are addresses that are provided via hardware such as a series of switches or cables. A soft address is an address that is assigned to a device for a period of time. Soft assigned addresses can change each time system power is applied, or each time the system is reset.
Hard addressing enables priority schemes and device location. If an address can be depended on to be consistent and unchanging, priority schemes can be devised that allow certain networked devices to receive their communications quicker than other networked devices, allowing more important network packets to be routed first. Consistent and unchanging addresses also allow a physical mapping scheme. Hard addresses can be set or mapped to correlate with the physical slots in which the networked devices reside.
Among other uses, hard addressing is extremely beneficial whenever devices need to be serviced. Because the hard address correlates to a physical location, a malfunctioning device can be easily located. For example, disk arrays benefit greatly from a physical mapping scheme. Typically, the disks that form the array reside in specific slots within enclosures. Whenever a disk fails or produces errors, service personnel need to find that disk quickly. If the disk's physical slot address correlates with the disk's loop address, service personnel can quickly discover which disk is creating errors and locate its physical location so that it can be repaired or replaced.
Fibre channel arbitrated loop protocol (FC-AL) is an interconnection standard that was created to address the need for high-speed network connections that could support bandwidth-intensive data transfers. Fibre channel optionally provides support for switched point-to-point connections between communicating devices. Particularly with point-to-point communication, Fibre Channel networks require accurate and consistent addressing amongst the networked devices for efficient operation.
During initialization of a Fibre Channel network, one device is designated as a master and each successive device in the loop sets a bit within an allocation bitmap to claim a particular address. If all the addresses are unique and each device claims what the network expects it to claim, the network operates efficiently. However, if a fault occurs such as a fault in the networked device or a backplane, for example a fault caused by a bad pin or broken wire, the device will claim what appears to be a random address in the network. If that address conflicts with an address another device tries to claim, that device will also claim an unpredictable (i.e. soft) address.
The result of the aforementioned issues is a breakdown in the loop's addressing scheme. Such a breakdown interferes with planned prioritization and physical location mapping. The results are degraded network performance and the inability to easily locate the faulty device.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that automatically and transparently translate any soft addresses claimed by any network device to a hard or physical slot address, or any address that the network expects. Such an apparatus, system and method most beneficially would not require human intervention in order to ensure that the network addressing is consistent and assigned as expected.
Beneficially, such an apparatus, system, and method would improve an arbitrated loop network's reliability and efficiency by reducing down time by facilitating rapid identification and location of faulty devices. Such an apparatus, system and method would preferably be transparent to the networked devices on the loop so that regardless of the address that a networked device claims, the network may see the device at the desired address. Such an apparatus, system and method would prevent address conflicts on the network and enforce a consistent addressing and priority scheme.